I have two questions. My first question is can I edit a mod that I made without an active plugin? I am making a simple mod that simply changes the guards' outfit. I saved it and added it to my game. Then it worked and I made some more changes. I did it without having an active plugin and edited the mod that I made. I added it to the game and the new changes showed up, but not the old. So can I edit I mod that I worked on without an active plugin because I want the changes to affect the mod, not just the plugin. Secondly I can't find the cowl; I tried searching for it in the all section, but couldn't find it. How do I find it?

Answer to first question:

Because the Creation Kit is a rather silly piece of software, by default it won't let you modify anything added or modified by an esp in any meaningful way. So your new mod is completely overwriting all of the changes made by your old mod, using vanilla values for those attributes where you haven't made edits. Which is why your new changes are showing up, but your old ones are getting overwritten. It's a dumb system, because it automatically makes any two mods altering the same cell, NPC, or object incompatible, even if their edits would be wholly compatible if merged into a single esp.

Anyways. My opinion aside, if you want to edit an esp file, turn it into an esm master file using WryeBash. Right-click on the mod you want to edit in WryeBash, and select "esmify." Skyrim and the CK will now think that it is an esm file, and it will show up at the top of the data file list along with the other master files. Load it, make edits, save your new esp, and don't forget to revert the old mod you turned into an esm back into an esp, else Skyrim will start behaving in weird ways or something.

Second question:

It might be labled as "hood" or "hat."

If that doesn't work, can try manually going through the various categories. Vanilla and official DLC clothes are listed under Items > Armor. If it's something added by a mod, make sure the appropriate esp file has been loaded.

Ok thanks!

The active plugin is the esp that you are saving your changes into. To create a new esp, you start with no active plugin and when you save your work, the CK will create a new esp for you when you exit. It sounds like that was where you started. Then to go back and make more changes to that esp, you make it the active plugin by selecting it and checking it as the active plugin. When you make changes and save, the changes are saved into the active plugin - your esp. That is how it works. Plain and simple.

When you made more changes without setting your original esp as the active plugin and then saved them, you probably saved right over the original esp - assuming you gave it the same name.